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### K and Kc

Posted: Tue Jan 08, 2019 9:44 pm
Can someone explain to me the difference between K and Kc? When do you use one over the other? (I thought of this while looking at Topic 5H.3 or page 412 of the 7th edition book, just in case this helps)

### Re: K and Kc

Posted: Tue Jan 08, 2019 9:50 pm
The way I understood it, Kc is for molar concentration. There's also Kp but that's for partial pressures for gases. I think K is just the equilibrium constant and Kc is just a more specific way of denoting what you are finding.

### Re: K and Kc

Posted: Wed Jan 09, 2019 11:20 am
Kc is specifically the molar concentration [P]/[R], and K is just an overall equilibrium constant.

### Re: K and Kc

Posted: Wed Jan 09, 2019 11:47 am
I think that when just K is listed it usually is referring to Kp because the pressures give a more accurate value than the concentrations

### Re: K and Kc

Posted: Wed Jan 09, 2019 12:03 pm
Do we need to memorize the formula in the book for converting between the 2?

### Re: K and Kc

Posted: Wed Jan 09, 2019 12:42 pm
Jordan Lo 2A wrote:Do we need to memorize the formula in the book for converting between the 2?

My guess would be no, because we rarely if ever have to memorize any formulas.

### Re: K and Kc

Posted: Wed Jan 09, 2019 3:57 pm
Jordan Lo 2A wrote:Do we need to memorize the formula in the book for converting between the 2?

The only formula you need anyway to convert between the two is the ideal gas law, PV=nRT which changes to P=concentrationRT. It's handy to know, but I don't think you need to memorize it.

### Re: K and Kc

Posted: Wed Jan 09, 2019 4:15 pm
K and Kc are the same thing but K can also represent Kp

### Re: K and Kc

Posted: Wed Jan 09, 2019 4:48 pm
You can determine whether you should be using Kc or Kp depending on the states of the molecules in the chemical equation, or also the information given to you.